This invention relates generally to surgical devices, and more particularly to medical devices for controlling the flow of fluids through catheter introducers and other sheaths, cannulae, catheters, trocars, scopes and the like.
It is now well known to perform a variety of surgical procedures by the introduction of an interventional device into the body, for example, into an arterial or venous blood vessel, or into a laparoscopic or other cavity artificially maintained in the body. Typical of the former type of procedure are coronary angiography (e.g., where an X-ray contrast fluid is inserted into the coronary artery) and percutaneous transluminal coronary angioplasty (PTCA). These and other procedures involve the introduction of an interventional device, such as a catheter (open or closed end), a wire guide, a balloon, a stent, an atherectomy device, or the like into the vessel or cavity in question. The single generic term xe2x80x9ccatheterxe2x80x9d should be understood herein to include all of such interventional devices, unless the context limits the meaning of the term.
Procedures for introducing a catheter into a blood vessel include the cut-down method and the Seldinger technique. The Seldinger technique is well known, and first involves opening a blood vessel with a needle, inserting a guide wire into the vessel through the lumen of the needle, withdrawing the needle and inserting a dilator over the guide wire. The dilator is located inside an associated sheath which is also inserted into the vessel, and the dilator is sealed to the sheath by a hemostasis or hemostatic valve through which the dilator passes. The dilator is removed, and the catheter inserted through the sheath and hemostatic valve into the vessel.
During the performance of the Seldinger technique and other procedures, care must be taken to avoid the undesirable introduction of air into the vessel (air embolism) and the undesirable leakage of blood, other fluids or a cavity-pressurizing gas from the patient (as much for the protection of health care practitioners as of the patient). As procedures for introducing catheters and other interventional devices have become more widely accepted, the procedures have also become more diverse, and the variety of sizes and types of devices employed has grown dramatically. The risks of inward or outward leakage thus become greater.
Because of such variety in the sizes and types of catheters and other devices to be handled, it would be highly desirable to have a hemostatic seal or other check valve which seals an introducer sheath or other device with a high degree of effectiveness when no catheter or other interventional device lies across the seal or valve, and which is also capable of providing an acceptable seal to catheters and other interventional devices having a wide range of diameters. High resistance to tearing when penetrated by catheters and other interventional devices of large diameter is very desirable as well. It would also be valuable to have a hemostatic seal or other check valve which allowed the easy passage through the seal or valve of devices of a very wide range of diameters, without interfering with tactile feedback from the catheter or other interventional device. Such tactile feedback is also known simply as xe2x80x9cfeel.xe2x80x9d It would also be desirable to have a hemostatic seal or other check valve which tolerated repeated insertions and withdrawals of catheters or other interventional devices without any appreciable decrease in the performance characteristics of the seal or valve, especially with respect to leakage and xe2x80x9cfeel.xe2x80x9d
A variety of prior devices are known to act as hemostatic or check valves. For example, U.S. Pat. No. 5,273,546 (McLaughlin et al., Dec. 28, 1993) discloses a hemostasis valve including an elastomeric gasket, the gasket having at least one concave surface and a pin hole or slits through the central region of the gasket. The gasket is preferably composed of polyisoprene, but could also be composed of silicone rubber, natural rubber or a thermoplastic elastomer, such as an injection moldable synthetic rubber compound. The gasket material has a hardness of 30-50 Shore A, preferably 35-45 Shore A. One drawback of silicone rubbers and other materials of similar hardness is that such materials offer an inadequately soft and compliant texture, so that the xe2x80x9cfeelxe2x80x9d of the catheter or other interventional device is less than adequate when the catheter or device is rotated or advanced. Selecting a silicone rubber of lower hardness is inadequate because the very low durometer silicone materials (below a hardness of 30 Shore A) do not currently offer the degree of resistance to tearing which would make the valve acceptably durable for surgical use.
U.S. Pat. No. 5,141,498 (Christian, Aug. 25, 1992) is directed to a flexible valve which includes a body having a cylindrical wall with a central bore therein, and at least three flexible leaflets adjoining the central wall. The valve body is composed of an elastomeric material, for example, a urethane compound having a hardness of 20-50 Shore A, preferably 35 Shore A. The patent notes that a xe2x80x9crubber-likexe2x80x9d compound identified as xe2x80x9cKraytonxe2x80x9d can also be used. The valve of the reference is intended to remedy the specific drawbacks associated with the so-called xe2x80x9cduckbillxe2x80x9d type of valve having only two of such leaflets. Duckbill valves are well known to be subject to several drawbacks, not all of which are mentioned in the patent. First, duckbill valves sometimes invert when relatively large diameter catheters or other interventional devices are inserted through them and then withdrawn. Moreover, they sometimes possess a large well behind them which can trap air or blood therein; this well cannot be flushed out in the conventional manner, that is, by injection through the side arm (or extension tube) commonly present in devices incorporating hemostatic valves. Finally, duckbill valves commonly are unable to maintain a seal under a negative pressure or vacuum. This is seen, for example, when a health care practitioner draws on a syringe connected to the side arm; air is undesirably drawn through the valve and into the syringe and the body containing the valve. The Christian patent thus uses compounds of a specific type (along with the additional leaflet) to cure problems associated with a specific valve construction, and makes no general teachings about such compounds which would apply to other types of valves. Moreover, the patent does not appear to disclose or suggest that all of the indicated compounds were in fact useful over the entire range of hardness specified.
U.S. Pat. No. 5,025,829 (Edwards et al., Jun. 25, 1991) is directed to a parenteral check valve including a preloaded, perforate disk made of a thermoplastic elastomer, an elastomeric material or a thermoplastic material having a hardness of 35 to 100 Shore A. An example of such a material is a xe2x80x9cKRATONxe2x80x9d brand thermoplastic elastomer. (xe2x80x9cKRATONxe2x80x9d is believed to be a registered trademark of Shell Chemical Company.) The disk seals against a circular flange or ring on a perforate seat in the valve; fluid pressure moves the disk away from the flange to allow fluid flow through the perforation in the disk.
Finally, U.S. Pat. No. 5,342,315 (Rowe et al., Aug. 30, 1994, incorporating by reference the application leading to U.S. Pat. No. 5,545,142, Stephens et al., Aug. 13, 1996) discloses a variety of trocar seals made from elastomeric materials such as silicone, latex, rubber, polyurethane, xe2x80x9cKratonxe2x80x9d (specifically, a thermoplastic elastomer of A-B-A type, in particular, styrene-isoprene-styrene block copolymer) or the like. It is believed that S-I-S type block copolymers typically have a hardness of 30 to 40 Shore A, comparable to the other identified elastomers, all of which lack the durability and resistance to splitting desirable for hemostatic valves and other check valves.
Again, it would be highly desirable to have a hemostatic valve or other check valve which overcomes the various drawbacks associated with these and other devices, as noted above.
According to the present invention, there is a valve arrangement for controlling the flow of fluid through a medical device, wherein the arrangement comprises a seal to be disposed in the fluid flow, at least one perforation to be found of the seal at least in the region of the or each perforation to close the perforation(s). The material can be compressible, and the means can be designed to deflect the material of the seal, at least in the region of the or each perforation, in order to close the perforation(s) whenever the seal is unpenetrated by the medical device. The seal can be mounted in order to be changed between one state and another state, so that when the seal is in the one or undeflected state, the perforation(s) is open to permit fluid flow, and when in the other or deflected state, the perforation(s) is closed to prevent fluid flow, and in which the means serves to transfer the seal between the states. The material can be of low durometer thermoplastic. Alternatively, in another aspect of the invention, the material of the seal can be of resilient material whereby the seal can be moved between a concave state and a convex state, and wherein the or each perforation is formed in such a manner that the perforation(s) is open in one of the states and closed in the other of the states.
Each perforation(s) can be rectangular in shape and can be lined with a softer material in order to ensure total closure of the perforation(s), even when instruments are passed therethrough.
In yet another aspect of the invention, the foregoing problems are solved and a technical advance is achieved in an illustrative fluid flow check valve, or valve for sealing catheter introducers and the like. The valve of the present invention includes a perforated disk seal which is deflected so as to possess a concave face in the proximal or upstream direction. The disk seal is composed of a low durometer thermoplastic material, preferably a styrene-ethylene/butylene-styrene block copolymer, having a hardness of no more than about 30 Shore A. Unexpectedly, the seal of the present invention is highly resistant to tearing or splitting when repeatedly penetrated by catheters or other interventional devices which would render silicone or other rubber seals of similar hardness useless. Not only is the seal of the present invention resistant to such splitting, the seal also maintains a very good fluid seal against the periphery of the catheter or other inserted device. The present invention is particularly advantageous over the prior art in that it achieves these functions while simultaneously permitting the health care practitioner very good xe2x80x9cfeelxe2x80x9d of the catheter or other device introduced through the seal.
In one aspect, then, the present invention is directed to a valve for a fluid flow path of a medical device, comprising: a seal disposed in the fluid flow path, the seal being composed of a very low durometer thermoplastic styrenic elastomer having a hardness of no more than about 30 Shore A, and the seal having an unstressed condition in which the seal is shaped generally as a disk and has opposed first and second faces and at least one perforation extending through the seal from the first face to the second face; and means connected to the fluid flow path for deflecting the seal so as to close the at least one perforation in the seal.
The first and second faces of the seal define a distal or downstream preferred direction of movement through the at least one perforation through the seal. Such movement is by a catheter or other interventional device when the valve of the present invention is incorporated into an introducer sheath or the like, or by fluid when the valve is a fluid flow check valve.
Preferably, the seal is composed of a thermoplastic styrene-ethylene/butylene-styrene (SEBS) block copolymer having a hardness between about 2 Shore A and 30 Shore A, and more preferably, a hardness of about 13 Shore A to 15 Shore A. Such thermoplastic elastomeric block copolymers have been found to withstand repeated penetrations by catheters and other interventional devices of a wide variety of sizes without tearing or leaking. Materials incorporating xe2x80x9cKRATONxe2x80x9d G polymers have been found particularly useful for this purpose. (As noted above, xe2x80x9cKRATONxe2x80x9d is believed to be a trademark of Shell Chemical Company for polymers.)
Also preferably, the deflecting means imparts a concave shape to the first face of the seal, that is, the face that faces outwardly from the valve and which is first penetrated by the catheter or other interventional device. Such a shape has been found to be very important in preventing inversion of the seal during or after rotation or distal movement of the catheter or other device, thereby avoiding undesired leakage from the introducer sheath. A convenient deflecting means for shaping the seal in this manner comprises a valve body defining at least part of the flow path, a valve seat formed in the valve body and a cap engageable with the valve body adjacent to the valve seat. The seal is received between and its periphery is compressed and clamped between the cap and the valve body, preferably, between the cap and the valve seats as well as deflected distally.
The concave shape of the seal can be maintained or augmented by a facing pair of annular flanges located one each on the cap and valve seat, each of the flanges abutting a face of the seal. The cap flange can be formed integrally, that is, as a unit with the remainder of the cap. It is convenient, however, to form the flange on a separate ring received in the cap. The ring is positioned in the opening in the cap through which the catheter or other interventional device is inserted into the flow path.
It is highly preferred that the valve seat is formed as a series of steps in the valve body, the steps decreasing in radius in the distal or downstream direction.
It is also highly preferred that, when the seal is in its unstressed condition, the at least one perforation through the seal is wider at the second face of the seal (the distal or downstream face) than it is at the first face (the proximal or upstream face). The at least one perforation can be Y-shaped in cross-section but can possess a substantial length transverse to that cross-section. Such a perforation is referred to as xe2x80x9cY-shaped.xe2x80x9d The at least one perforation can alternatively be circular or oval in shape.
In another aspect, the present invention is directed to a device of the type disclosed above, comprising a number of the distinct elements described above. In particular, in this aspect the present invention is directed to a valve for a fluid flow path, comprising: a seal disposed in the fluid flow path, the seal being composed of a very low durometer thermoplastic elastomeric styrene-ethylene/butylene-styrene block copolymer having a hardness of no more than about 30 Shore A, and the seal having an unstressed condition in which the seal is shaped generally as a disk and has opposed first and second faces and at least one perforation extending through the seal from the first face to the second face; and means connected to the fluid flow path for deflecting the seal so as to close the at least one perforation in the seal; wherein the deflecting means comprises a valve body defining at least part of the flow path, a valve seat formed in the valve body and a cap engageable with the valve body, the periphery of the seal being compressed and clamped between the cap and the valve seat; and wherein the cap and the valve seat each include respective annular cap and valve seat flanges facing each other and abutting the first and second faces of the seal, respectively, imparting a concave shape to the first face of the seal; wherein the first and second faces of the seal define a preferred direction of movement through the at least one perforation, and wherein the deflecting means imparts a concave shape to the first face of the seal facing opposite the preferred direction of movement through the at least one perforation; and wherein when the seal is in its unstressed condition, the at least one perforation is wider at the second face of the seal than at the first face of the seal.
In yet another aspect, the present invention is directed to an improvement in a valve for a fluid flow path, the valve including a perforate elastomeric disk closing the flow path, the improvement wherein the disk is composed of a thermoplastic styrene-ethylene/butylene-styrene block copolymer having a hardness of no more than about 30 Shore A.
In still another aspect, the present invention is directed to an improvement in a self-sealing, penetrable, hemostatic valve for an introducer for a catheter or other interventional device, the catheter or other interventional device having a proximal end, and the valve including a generally disk-shaped seal receiving and sealing around the periphery of the catheter or other interventional device when inserted in the introducer, the improvement wherein the seal is composed of a thermoplastic styrene-ethylene/butylene-styrene block copolymer having a hardness of no more than about 30 Shore A, and wherein the seal is deflected so as to present a concave face towards the proximal end of the catheter or other interventional device.
The valve of the present invention is particularly advantageous over prior seals in that it possesses a high degree of effectiveness when no catheter or other interventional device lies across the seal or valve, and simultaneously provides an acceptable seal to catheters and other interventional devices having a wide range of diameters. The valve of the present invention also possesses a high resistance to tearing when penetrated by catheters or other interventional devices of large diameter. The valve of the present invention allows the easy passage devices of a very wide range of diameters without interfering with tactile feedback from them. The valve of the present invention seals well against vacuum or a negative pressure. The valve of the present invention tolerates repeated insertions and withdrawals of catheters or other interventional devices without any appreciable decrease in the performance characteristics of the seal or valve, especially with respect to leakage and xe2x80x9cfeel.xe2x80x9d Finally, the valve of the present invention is advantageous in that the distal or inward deflection of the seal along with compression placed upon the seal by clamping of its periphery prevents undue inversion of the seal surface despite repeated removals and manipulations of devices lying across the valve.